Lady Flat

Lady Flat, a member of the Demonic Nobility, was introduced in episode 2/3 in the town of Perstity with her twin brother Sharp. At the time, they had been there to find Lilette and take her back to Nifhliem. Since then, she had been working with the demons to free the race from being trapped in the underworld as an assistent to Melody and Sonata. In episode 19, however, it was revealed that she had a change of heart and joined the Judges and Lilette. It is hinted that this change of heart was caused by romantic feelings toward Feliciano.

The only person in the series that she is shown to have been with since birth is her brother, Sharp. She described Melody as being more of a partner than a friend in a conversation with Feliciano, and Sonata as her boss. When she left the demons and joined the Judges, she became more friendly with Lilette and the Allies/Axis. It is implied throughout the series and later proved to be cannon that Flat has romantic feelings for Feliciano.